1. Field of the Invention
The present invention relates to an optical disk apparatus.
2. Description of the Related Art
There are optical disks such as a compact disk-read only memory (CD-ROM) and a digital versatile disk-read only memory (DVD-ROM), which are for playback only; a compact disk-recordable (CD-R), a digital versatile disk-recordable (DVD-R), and a digital versatile disk+recordable (DVD+R), which are recordable; and a compact disk-rewritable (CD-RW), a digital versatile disk-rewritable (DVD-RW), a digital versatile disk+rewritable (DVD+RW), and a Blu-ray disc (BD), which are rewritable.
The recordable optical disks such as a CD-R and a DVD-R and the rewritable optical disks such as a CD-RW and a DVD-RW are different from the playback-only optical disks such as a CD-ROM and a DVD-ROM in that a groove track and a land track are pre-formed on a recording surface of the recordable optical disks and the rewritable optical disks, but not of the playback-only optical disks. A groove track is wobbled in a predetermined cycle, so that wobbles are formed at both margins thereof in the predetermined cycle, respectively. A wobble signal is detected from a wobble so as to be used for controlling rotation of an optical disk and generating a recording clock. Hence, when a wobble signal is of high quality, data can be recorded at high quality without reducing its video quality and audio quality.
Conventionally, a band-pass filter which a wobble signal detection circuit to detect a wobble signal has is adjusted such that the amplitude of a signal which passes through the band-pass filter becomes largest.
More specifically, there is known an optical disk apparatus in which the amplitude of a signal which passes through a band-pass filter is measured, and the band-pass filter is adjusted such that the amplitude thereof becomes largest. (For example, refer to Japanese Patent Application Laid-open Publication No. 2005-116148 (hereinafter Patent Document 1).)
Patent Document 1 also describes an optical disk apparatus in which the jitter of a signal which passes through a band-pass filter is measured, and the band-pass filter is adjusted such that the jitter thereof becomes smallest.
In order to detect a highest-quality wobble signal, it is preferable that, like the optical disk apparatus of Patent Document 1, the jitter of the signal be directly measured, and the band-pass filter be adjusted such that the jitter thereof becomes smallest.
However, adding an element such as a jitter measurement circuit to an optical disk apparatus is required to measure jitters. As a result, a problem arises that a manufacturing cost and the like of an optical disk apparatus increases.